The invention relates more particularly to a circuit breaker having a blast cylinder and a second chamber in which an additional pair of contacts is capable of generating a secondary arc during circuit breaker opening, with the secondary arc being used to provide energy for the opening operation.
Such a circuit breaker is described, for example, in published French patent No. 2 610 763.
A problem that needs to be solved in this type of circuit breaker is that the pressure in the blast cylinder is low when interrupting small currents (low operating energy) and that the pressure is high when interrupting large currents without there being a corresponding increase in the available operating energy.
This problem has been partially solved in published German application No. 23 49 263.
In this document, provision is made to maintain the pressure in the blast cylinder at a low value by providing the blast piston with closable openings.
The circuit breaker described in the above-mentioned document nevertheless suffers from drawbacks. In the prior art circuit breaker the maximum separation distance between the secondary contacts is as long as the separation distance between the arcing contacts causing the secondary arc to be drawn out lengthwise, thereby giving rise to arcs being struck on the walls of the chamber containing the secondary contacts.
This type of arcing impedes good current interruption and increases the rate of the circuit breaker wear.
A first object of the invention is to provide a circuit breaker in which the secondary arc does not strike further arcs.
In the prior art circuit breaker, no steps are taken to prevent an arc being struck when the circuit breaker is closed. However, such arcing increases the operating energy required and gives rise to additional circuit breaker wear.
Another object of the invention is to provide a circuit breaker in which no arc is struck during circuit breaker closing.